In respirators, especially in gas masks and breathing equipment, respiration takes place in a closed circuit to reduce the weight and to increase the use time, and only the amount of oxygen consumed is replaced from a pressurized gas reservoir and fed into the circuit. Enrichment of the carbon dioxide (CO2) breathed out in the circuit to physiologically harmful levels in the circuit must be avoided. An absorber with an absorbent, which extracts the CO2 from the breathing circuit, is present for this in the circuit. Prior-art absorbents consist of one or more alkali hydroxides and contain or consist especially of calcium hydroxide. The absorbents are contained in respirators in a breathing lime absorber, a so-called alkali cartridge used as a replaceable part. Heat and moisture are generated during the chemical reaction taking place between the CO2 and the absorbent. The heat leads to a rise in the breathing gas temperature and may thus lead to a physical compromise for the person respirated by means of the respirator. Temperatures 25° C. above the ambient temperature were measured in experimental measurements in the breathing gas saturated with moisture at the outlet of the breathing lime absorber.
One solution to eliminate this problem is to condition the breathing air in closed-circuit gas masks and breathing equipment, which are used for a use time of several hours, i.e., to both cool the breathing air and reduce the quantity of moisture in the circuit.
The cooling of the breathing lime absorber with the use of paraffin or the use of a salt as a coolant for such respirators is disclosed in DE 879 851 B, where the evaporation or melt temperature is between 40° C. and 180° C. and the breathing lime absorber is surrounded by the coolant. The breathing lime absorber is used as a heat exchanger rather than the breathing gas being cooled directly. The use of a separate heat exchanger, in which the exchange of the amount of heat is brought about by the motion of the air generated by the breathing bag, is known from U.S. Pat. No. 4,635,629. The exchanged amount of heat is thus not adapted to the breathing gas temperature and cannot be influenced by a control circuit. Cooling of the breathing lime absorber with an evaporating agent by means of the external evaporative cooling via the housing of the lime absorber is known from DE 10304394 B4 (U.S. Pat. No. 6,990,979). The use of a fan is known from the same document DE 10304394 B4 to increase the amount of air and to improve as a consequence the heat exchange.